Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu
The warm weather has moved us ahead of schedule for small grains. That means we need to start thinking about disease management. Here are my, “Top 5” small grain disease management tips:
#1 Know your variety. Keep records of your wheat varieties in an easily accessible location. Make sure to note how they are rated for potentially damaging diseases including a) Leaf Blotches (tan spot and Stagonospora); b) Fusarium head blight; c) Powdery mildew; d) rusts, including stripe rust. We learned last year the importance of knowing the disease rating of your varieties in relation to stripe rust. Growers planting susceptible varieties (Dynagro Shirley is a good example) saw stripe rust develop early in some places and benefitted from fungicide intervention. Growers who planted a variety with good resistance did not need to apply a fungicide for stripe rust, and instead could focus on other disease issues. Remember, the difference in resistance to stripe rust is huge – with little to no disease development in MR to R varieties (Fig. 1).
#2 Scout your fields. Make sure you are taking the time to check your fields every week or so, and increase scouting as fields approach heading. You don’t want to be caught off guard by a flush of disease or pests such as cereal leaf beetle.
#3 Consider a fungicide application. Regional data show that you can see, on average, a 3-8 bu/A yield improvement when a fungicide is applied at either flag leaf emergence or flowering. A premix fungicide is your best bet at flag leaf, and there are many good products available. If applying at flowering in order to target glume blotch and fusarium head blight, Caramba, Prosaro, and Proline are your best bets. You can also use a labeled tebuconazole product, but these will not provide much protection against fusarium head blight and DON. It is also important to note that we have seen that the flower timing is efficacious in terms of protecting overall yield, as well as quality. This is likely because our most common foliar diseases, the leaf blotch diseases (Stagonospora and tan spot) take longer to develop in many cases and do not reach the flag leaf until later in the season. If you recall, several years ago, it was not uncommon to put on your fungicides at full head emergence instead of flag leaf emergence. This protected the flag leaf and glumes, but did not protect against fusarium head blight. Now, we know that the QoI’s (strobilurins-FRAC group 11) can make DON worse, especially if applied to the head, and therefore want to avoid these timings if possible. Caramba, Prosaro, and Proline all will provide control against foliar diseases, and our data have showed no significant yield difference when comparing these products applied at flower to other products applied at flag leaf emergence. Look for some new products for safe application to flowering wheat in the next 1-2 years. On a similar note, for those who want to include a cut rate of a premix fungicide or a cheap DMI early in the season with your nitrogen- try to get these applied as close to jointing as possible. Diseases need canopy humidity and warmer temperatures to begin to develop, and fungicides applied too early will run out of gas before disease potential starts.
#4 Pay attention to regional forecasts and disease reports. There are several ways for you to stay up to date on any impending disease issues. The WCU is one avenue. Also you can sign up for email or text notifications to updates to the Field Crop Disease Management Blog (http://extension.udel.edu/fieldcropdisease/). Make sure to sign up for the Fusarium Head Blight Prediction Center for updates on FHB (http://www.wheatscab.psu.edu/).
#5 If you have an issue- have it confirmed. Call your county agricultural Extension agent, the UD Diagnostic Clinic, or myself if you have any issues during the season that need to be addressed. We can help with diagnosis and management recommendations. You don’t want to add an additional input to control something that was not disease related!
Figure 1. An example of wheat varieties with different levels of resistance to stripe rust. S/MS = susceptible; MR/R = resistant. Resistant varieties can show symptoms, but there will be fewer lesions, smaller lesions, and fewer spores produced within a lesion, resulting in a dramatically reduced impact on disease development and impact to yield.